# Metadata Source URL:: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6751071/ Topics:: #health --- # Effects of light on human circadian rhythms, sleep and mood Humans live in a 24-hour environment, in which light and darkness follow a diurnal pattern. Our circadian pacemaker, the suprachiasmatic nuclei (SCN) in the hypothalamus, is entrained to the 24-hour solar day via a pathway from ... ## Highlights > [!quote]+ Updated on 201022_100517 > > Rather recently, the availability of artificial light has substantially changed the light environment, especially during evening and night hours. This may increase the risk of developing circadian rhythm sleep–wake disorders (CRSWD), which are often caused by a misalignment of endogenous circadian rhythms and external light–dark cycles > [!quote]+ Updated on 201022_100539 > > On the other hand, light can also be used as an effective and noninvasive therapeutic option with little to no side effects, to improve sleep, mood and general well-being > [!quote]+ Updated on 201022_100600 > > The antidepressant effect of light is most pronounced when it is administered in the early morning hours > [!quote]+ Updated on 201022_100714 > > Previous cataract surgery or lens removal > [!quote]+ Updated on 201022_100739 > > Light at the wrong time may disrupt circadian rhythms and sleep, but in the form of light therapy, light exposure can be used as an intervention for psychiatric and other medical conditions.